Process of separating metals in solution.



UNITED STATES PATENT OFFICE.

HERBERT H. DOW, OF MIDLAND, MICHIGAN, AND WALTER S. GATES, OF WORTHINGTON,

ONTARIO, CANADA, ASSIGNORS TO THE ONTARIO NICKEL COMPANY, LIMITED, OF WORTH- INGTON, CANADA, A CORPORATION.

BROCESS OF SEPARATING METALS IN SOLUTION.

Specification of Letters Patent.

Patented March 2, 1909.

Application filed April 27, 1907. Serial No. 370,741.

To all whom it may concern:

Be it known that we, HERBERT H. Dow

and WALTER S. GATES, both citizens of the United States, residents of Midland, county of Midland, and State of Michigan, and Worthington, district of Algoma, and Province of Ontario, Canada, respectively, have invented a new and useful Improvement in Processes of Se arating Metals in Solution, of which the to owing is a specification, the principle of the invention being herein explained and the best mode in which we have contemplated ap lying that principle, so as to distinguish it rom other inventions.

Our invention relates to processes of separating metals and especially to a separation of the same, each substantially free of all the others, when contained in a water solution.

Said invention consists of ste s hereinafter fully described and speci cally set forth in the claims.

The improved results obtained b our new process are eflected by reason of the fact themselves within reasonable limits, an

there be present in the original solution enough of the metal, which upon the addition of the rea ent forms the more insoluble compound, to e at least a chemical equivalent of the reagent, then, the more insoluble precipitate is purified of its inclusions of the slightly less insoluble precipitates of the other metals by subjecting the ori inal solution and precipitates to a prolonge agitation b means of which the soluble com ound oi the metal forming the more insolubie preci itate reacts with the precipitates of the other metals to form soluble compounds of said other metals and more of the insoluble precipitate which is being purified.

We find a particular application for our improved process in the se arating of iron, copper ant nickel from eaci other, each in the form of a precipitate substantially free of the others, when all are contained in the same original water solution.

We are aware that iron, copper and nickel have been taken from a water solution in the same order and by the same reagents that we use, but we are not aware that products anywhere nearly pure have been obtained in the manner embodying our improved process. However, in fact we do know that large amounts of the valuable metals have been lost in the iron precipitate in other processes.

The fact is well-known that, if two metals are present in a solution, and one of the metals forms a preci itate or an insoluble compound more inso uble than the corresponding compound of the second metal, and there. is added to the solution the proper amount of a reagent capable of throwing down the first metal as a precipitate, then, said precipitate will in many cases carry down with it in insoluble formpart of the second metal. This will ha pen, first, always in case the second meta is also capable of being precipitated by the reagent said second metal is not capable of being so precipitated.

As an example of the first case, if a solution of iron an nickel is treated with calcium either metal alone, and thereagent is added in the proper amount to precipitate the iron, the iron recipit'ate will always carr down some inso uble nickel. As an examp e of the second case, if a solution of iron and nickel, with ammonium chlorid present, be treated with ammonium hydrate, which reagent will preci itate iron alone with ammonium chlorid, ut which will not precipitate nickel alone with ammonium chlorid, and the reagent be added in the proper amount to precipitate the iron, the lI'OIl preclpitate Wlll. always carr down some insoluble nickel. In'both of tli ese cases, if the nickel were not present in the original solution in an amount much greater than the iron, the iron will redominate in the preci itate because erric hydrate is more insolu le than nickel hydrate. The usual way in which these precipitations would be made in the laborator would be to add to the solution of iron an nickel in a beaker the proper amount of rod until the mixture became homogeneous and then stop, the idea being that the reel 1- tation of a certain amount of nicke 1n t e reagent and agitate by means'of a stirring which is used, and secondly, often even if hydrate, which reagent will precipitate dissolve nickel iron was unavoidable and irremediable exthat a slow subsequent action is possible by agitating the mixture in the presence of an excess of soluble salt of the metal forming the more insoluble precipitate, in this case iron. It has always been considered impossible to get the iron out free of copper and nickel and in fact has been considered necessary to take out the iron by means of a weak alkali (followed by a strong alkali for the nickel) or else the iron precipitate would contain a-very large amount of nickel.

By our im roved method the iron may be preci itated y as stron an alkali as is used or t e nickel, in fact a three metals, iron, copper and nickel, may be removed by the same reagent which may be strong or weak. The old method of purif 'ng such a precipitate of the included metal jsuch, for instance, as the purifying of ferric hydrate of inclusion of nickel hydrate, is to se arate the precipitate from the solution, issolve it, for mstance in an acid, and then re recipitate with a pro er amount of a suitab e rea ent, whereby a the'iron is a ain thrown own and containing some nicke but not so much of the latter as before, the difference of nickel being left in the second filtrate. The reason wh the nickel exists in the second filtrate in ess quantities than it does in the first is because in the acid solution it is in a more disseminated condition with regard to the iron than it was in the original solution, there being less nickel present, and only part of the nickel present being thrown down each time. Therefore a sufficient number of se arations' in sufiicientl dilute solutions w l accomplish a quantitative se aration, giving all the nicke inthe unite filtrate which will be very dilute. This method is commonly used in quantitative analysis,

and ordinarily four separations under good conditions are sui'ficient. Our method, how- .ever, as ordinarily practiced, while giving the precipitate practically pure, does not at one time remove from the solution all of the metal forming the most insoluble precipitate, because of the fact that the precipitate is afterwards purified by agitation in a solution containing an excess of a soluble salt of the metal which is being urified. Our method is, therefore, notav p icable to quantitative analysis, but is app icable to the commercial separation of metals from a solution which is eing supplied continuously to the cycle.

The followin description sets forth in detail certain m0 es of carrying out the invention, such disclosed modes constituting but a part of the various ways in which the principle of the invention may be used.

The a paratus required to carry out our improve rocess consists of any suitable form of agitating and containing tanks, and filtering or settling devices, and is the same for the separation of iron, copper and nickel as it is for other metals and substances.

We have devised several methods for carryin out our invention, each of which depen s for its improved result of obtaining substantially pure precipitates upon the comparative solu ilities of the substantially in-' soluble precipitates which are thrown down from the original solution when a reagent is added thereto in-an amount equal to the chemical equivalent of the metal which forms the more insoluble precipitate. Such invention is thus broadly set forth in our ending application Serial No. 300,728, iile February 12, 1906, Where three of the several methods to which allusion is here made are described in detail. 1 This our present aplpli cation relates s ecifically to one of t methods only. ing the separation of iron-copper and nickel consists in adding to a portion of the original solution of the three metals named, less than the chemical equivalent of rea ent capable of precipitating the iron as, or instance, powdered limestone. The result of such addition is the almost immediate precipitation from the solution of the major portion of the iron as an hydrate, but along with it, even in dilute solution, there is some copper and nickel thrown down as basic carbonates. A prolonged agitation of the precipitates in the original solution purifies the ironprecipitate of the included copper and nickel basic carbonates because of t e comparative insolubilities of the ferric hydrate and said basic carbonates, according to the following order of insolubility:'

Most insoluble FeQ ll Less insoluble CuCO CuO H and CuO H Least insoluble NiCO NiG H and Ni0,H

ZFeCl 3CaCO 3H,,() CuCl NiCl i 2FeO H +3CaCl +3CO +a little CuCO CuQ H a little NiCO NiO H +NiCh+ CuCl a little FeCl 3CuCO CuO H 4FeCl- 311 0 agitated his method of accomplish- 3NiCO more, in 01 3n,o agitated cNiCl 300 4FQO3H3.

After a prolonged agitation of the mixture of solution and precipitate, the ferric hydrate is found to" be substantially free of the included copper and nickel basic carbonates. Such purified iron precipitate is then separated out from the solution which will-contain in addition to all the copper and nickel, the portion of iron originally present in excess of the reagent added. To this solution,

containing thus a small amountof iron only, is added an additional quantity of the re-- agent in amount slightly in excess of that which is-required as a chemical equivalent of such remaining iron, which latter is thereupon precipitated as animpure recipitate containing copper and nickel su stantially in accordance with the equations last above given. Upon remov'ng such mixed precipitate, the solution is obviously left free of all iron. This mixed precipitate is ut with a will a uantity of precipitate which is ein puried in the manner 'ust described, w iereby the iron content of t e precipitate is purified of its inclusions of copper and nickel precipitate, by a prolonged agitation in the original solution, which contains of course an excess of soluble iron salt.

The solution of copper and nickel from which the iron has been thus removed is then agitated with calcium hydrate added to less than the chemical e uivalent of the copper present, the result eing the almost immediate precipitation of the major portion of the co per as hydrate, which latter however E0 contain some nickel hydrate. A prolonged agitation of this impure copper precipitate in the copper and nickel solution will purify said precipitate of the nickel because of the comparative solubilities of the The excess of the soluble copper salt in the original solution thus slowly dissolves the nickel hydrate contained in the insoluble cupric hydrate and precipitates in turn more cupric hydrate, the

, reactions being as follows:

CuCl NiCl CaO I-I CuO l-l CaCl.,+ NiCl a little CuCl a little NiO H N iO I-I CuCl agitated CuO H NiCl After a prolonged agitationof the mixture the cupric hydrate is found to be substantially free of the nickel hydrate. Such purified co per recipitate is then separated required asa' chemical equivalent of such remaining copper. The latter is thereupon precipitated'as an'impure precipitate, more or less nickel being included, and is thereupon removed to be further treated as had been the mixed iron precipitate in the preceding stage of the process. A pure solution of nickel obviously will remain, from which upon the addition of a suitable reagent such as the aforementioned calcium hydrate, all the nickel will be precipitated, free from the iron and copper, the reaction being:-

No prolonged agitation is, of course, necessary in connection with this last precipitation. The above method amounts in efl'eet, to the addition of the reagent in an amount just the chemical equivalent of the metal to be precipitated, since for example in the case of the copper and nickel present as impurities in the iron precipitate such metals act as a reagent during the purifying agitation to pro duce more of the soluble copper and nickel com ounds.

0 course it will be remembered that the separation takes place as well with the salts of the other mineral acids and mixtures as it does with the chlorid solutions.

It is contemplated in the above description that the method of treatment herein described, is applicable not alone to the separation of iron from nickel and copper, but also to thus separating aluminum and combinations of these two metals, as also iron in both conditions of oxidation.

\V e mean to include in the term nickel the nickel group of similar metals, viz. nickel and cobalt alone and together. I W e mean by the term prolonged agitation agitation for a length of time greater than that ordinarily required by a chemical rea ent to act on a solution which is capable of eing precipitated by it, and make the resulting mixture homogeneous.

We mean by the term chemical e uivaei lent of a reagent such an amount 0 that reagent as actually and finally enters into the reaction, since the cores of some particles of insoluble reagent might not react and it would be necessary, therefore, to add the reagent in a quantity in excess of that representing the theoretical chemical equivalent.

We mean by the term insoluble reci itates those that are more insoluble than t io hydrates of barium and calcium, for instance, thehydrates and carbonates of iron, aluminum, copper, nickel, etc.

It is a well-known law, of course, that the insoluble compounds tend to form and precipitate; for instance, the following reaction 1 naturally takes place immediately.

cecal, MgCl MgO H CaCl However, our improved process cannot be classified as coming solely under this broad head, but rather is a simultaneous dissolving to the very slight amount possible, of the more soluble component of a substantially insoluble mixture, and a precipitation from the solution of the other 'metal which is contained also as the more insoluble compound &

in the original insoluble mixture.

There are several reagents any one of which might be used in certain steps of our process. Instead of calcium carbonate in the precipitation of the iron, other alkaline earth carbonates and hydrates may be substituted, such as calcium hydrate and sodium hydrate. For the calcium hydrate in the copper precipitation there might be substituted such of the re uirecl amount of reagent be made alkaline or alkaline earth carbonates and hydrates as calcium carbonate, sodium hydrate and sodium carbonate. If any one of the three metals, iron, copper and nickel, is absent, thelother two may be separated and purified as described above, simply omitting.

the steps required by our process for that particu ar metal which is absent. For in stance, iron could be separated from nickel alone; from copper alone; or copper could be se arated from nickel alone.

' separation byour process. If, at any temperatures, solubilities so nearly identical that an econoimc separation is prevented. For instance, compounds of cobalt and nickel might have substantially the same solubilities at a temperature of 20 degrees; whereas at 60 degrees their solubilities might be so different as to allow of an economic time, more of the reagent is added than the chemical equivalent of the metal to be preci itated, the condition of equilibrium can e restored by the addition of more of the ori inal solution, which amounts, in effect, to t e adding of the chemical equivalent. k

Our method does not give dilute solutions and yet we obtain pure precipitates of the iron, copper and nickel, instead of the impure precipitates which are obtained by present methods, and the basic principle of our process is the purification of any precipitated metal or substance of the inclusions of other precipitated metals or substances slightly more soluble than the first, all of the precipitates being substantially insoluble-a though nothing is absolutely insoluble in a solventby meansof agitating such impure precipitate in a solution containing soluble salts of the more insoluble metal. We do not confine ourselves to the use of water as a solvent for obtaining the original solution. Where both or all of the metals in solution are capable of being precipitated by the reagent used, there has often been left and lost asmuch as 25% impurity, for instance, of nickel in the iron; Whereas, we are able, by our method, to free the iron precipitate entirely of the nickel impurity by a sufiiciently long and vigorous agitation. Such an impure iron precipitate may, for instance, be purified with vigorous agitation in one to four hours depending on conditions to a point where only 1% nickel remains. Our method, of course, works best on substances which, although insoluble, are colloidal and freely disseminated, since, thus, infinitely great surfaces are constantly presentedfor solution and subsequent immediate action of the soluble salt. I

We wish to point out that, if the addition so gradua y that it extends over a consider able length of time during which agitation is going on, this amounts in substance to adding the required amount of reagent and then, subjecting the mixture to prolonged agita tion. Finally, we should state that by the expression the metal which is being purifi'ed We mean the metal which we are trying at any particular stage in the process to remove as a precipitate free of the other metal consist in adding to the solution a reagent capable of producing a relatively insoluble precipitate with one of the metals, such reagent being added in an amount less than the chemical equivalent of said one metal; and then a itating the resultant mixture until any inc uded precipitates of the other metals are dissolved out 2. In a rocess of separating one metal substantia y free from another, such metals being contained in a solution, the steps which consist in adding to the solution a reagent capable ofproducin substantially insoluble 1precipitates with sai metals, one precipitate,

owever, varying from the other in its degree of solubility, such reagent being added in an amount less than the chemical equivalent of one of said metals; and then agitating the resultant mixtureuntil any inclusions of the .more soluble precipitates are substantially dissolved out.

3. Ina process of separating metals in solution, the steps which consist in adding to the solution a reagent capable of forming substantially insoluble preci itates with said metals, one precipitate, liowever, being slightly less soluble than the others, such reagent being added in an amount less than the chemical equivalent of such less soluble pre- I cipitate; and then agitating the mixture resu ting upon the addition of such reagent 1- intil any inclusions of the other recipitates are dissolved out of suchless solu le precipitate. a

4.- In a process of separating metals in solution, the steps which consist in adding to the solution a rea nt capable of forming substantially insolu le precipitates with said metals, one recipitate, however, being slightly less so uble than the others, such reagent being added in an amount less than the chemical e uivalent of the metal producsolution, the steps which consist in adding to, the solution a rea ent capable of forming -substantially inso uble precipitates with said metals, one recipitate, however, being slightly less solub e than the others, such reagent being added in an amount less than the chemical equivalent of the metal roducing such less soluble precipitate; a itating the mixture resulting upon the adc ition of such re-agent until such less soluble preciplitate is purified oi the inclusions of the er precipitate; removing such purified precipitate; adding to the remaining solution a quantity of such rea ent sli htly in excess of that re uired as a cIiemicaIequivalent of such 'meta remaining unprecipitated; and repeating the foregoing series of steps with the then remaining solution until all the metals are separated. 6. In a process, of separating metals in solution, the steps which consist in adding to the solution a reagent capable of producing a relatively insoluble precipitate with one of the metals, such reagent being added in an amount less than the chemical equivalent of said one metal; agitating the resultant mixture until the precipitate of said metal is purified of the inclusions ofthe other metals; addin to the remaining solution an amount of suc rea ent suflicient to actually precipi- 'tate the ba ance'of such first metal; adding the resultant im ure precipitate to another uantit of the first precipitate being puried in t e manner just mentioned. ,7. In a process of separatin metals in solution, the steps which consist in adding to the solution a rea ent capable of producing a relatively insolu le precipitate with one of the metals, such reagent being added in an amount less than the chemical equivalent of said one metal; agitating the resultant mixture until the precipitate of said metal is purified ofthe inclusions of the other metals;

addin to the remaining solution an amount of sue reagent sufiicient to actually precipi-' tate the balance of such first metal; adding the resultant im ure precipitate to another quantity of the iirst precipitate being puribed in the manner just mentioned; and repeating the foregoing series of steps with the then remaining solution until all the metals are se arated.

8. II. a process of separating metals in solution, the steps which consist in adding to the solution a rea ent capable of producing a relatively insolu le precipitate with one of the metals, such reagent being added in an amount less than the chemical equivalent of said one metal; agitating the resultant mixture until the precipitate of said metal is purified from inclusions of the other metals; addin to the remaining solution a quantity of suc reagent slightly in excess of thatrequired as a chemical equivalent of such first metal; and adding the resultant impure precipitate to another quantity of the first precipitate being purified in the manner just described.

9. In a process, of separating metals in solution, the steps which consist in adding to the solution a rea ent capable of producing a relatively insoluhle'precipitatewith one o the metals, such reagent being added inan amount less than the chemical equivalent of said one metal; agitating the resultant mixture until the precipitate of said metal is purified from inclusions of the other metals; addin to the remaining solution a quantity of suc 1 reagent slightly in excess of that required as a chemical e uivalent of such first metal; adding the resu tant impure precipitate to another quantity of the first precipitate being urified in the manner just mentioned am repeating the foregoing series of steps with the then remaining solution until all the metals are separated.

1.0. In a process of separating iron and nickel in solution, the steps which consist in adding to the solutiona reagent capable of producing an insoluble precipitate with the iron, such reagent being added in an amount less than the chemical equivalent of the iron; and then agitating the mixed solution and precipitate until any inclusions of nickel precipitate are substantially dissolved out.

11. Inca-process of separating iron and nickel in solution, the steps which consist in adding to the solution a reagent capable of producing an insoluble precipitate with the iron, such rea ent being added in an amount less than the c emical equivalent of the iron; agitating the resultant mixture until the iron preci itate is purified of any inclusions of nicke removing such purified precipitate; addin to the remaining solution an amount of suc rea ent sufiicient to actually reci itatethe ba ance of the iron; and ad( ing t e resultant im ure precipitate to another guantity ofte first precipitate being puried in the mannerjust' mentioned.

12. In a rocess of separating iron, copper,

and nickel 1n solution, the steps which consist in adding to the solution a 'rea ent capable of producinga relatively insolu le preci 'itate with the iron, such reagent being a ded in an amount less than the chemical equivalent of the iron; agitating the resultant mixture until the iron precipitate is purified of any inclusions of copper and nickel; adding to the remaining solution} an amount of such reagent sufiicient to actually precipitate the balance of the iron; adding the resultant im ure precipitate to another- Euantity. of the st precipitate being uried in the manner-just mentioned; an repeating the foregoing series of steps with the then remaining solution to similarly re-- move .the copper and leave a pure solution of nickel. t

' 13. In a process of separating iron and nickel in solution, the steps which consist in adding to the solution owdered limestone in an amount less than t e chemical equivalent of the iron, whereby the major portion of the latter is precipitated as ferric hydrate;

agitating the resultant mixture until the iron precipitate is purified of any inclusions of nickel; removing such purified precipitate;

addingto the remaining solution an amount of the limestone sufiicient to actually precipitate the balance of the iron whereby a pure solution of nickel is left; and adding the resultant impure precipitate to another quantity of the first precipitate being purified in the manner just described; I

14, Ina rocess of separating iron, copper and nickel in solution, the steps which consist in adding to the solution powdered lime:

other uantity of the first precipitate being purifie in the manner just described; treatmg the solution of copperandnickel' with calcium hydrate in an amount less than the chemical equivalent of the copper therein; and then purifying the resultant p'rec' itate and solution in the same manner as be ore.

Signed by HERBERT H. Dow,this 19th day of April, 1907.

Attested b D. T. AVIES,

JNOpF. OBERLIN. Signed by WALTER S. GATES, this 2'day of'April, 1907.

WALTER S. GATES.

Attested b d A. N. ATRIAROKE,

O. J. STROSACKER..

" HERBERT-H. owv 

